Eventual consistency intent cleanup in a dispersed storage network

ABSTRACT

A method for execution by a dispersed storage (DS) cleanup unit includes determining a dead session of a DSN. A subset of a plurality of eventual consistency intent names is generated by identifying eventual consistency intent names that include a session identifier corresponding to the dead session in a prefix of the eventual consistency intent names, where the subset of the plurality of eventual consistency intent names corresponds to all eventual consistency intents of the dead session. A subset of storage units responsible for storing the all eventual consistency intents of the dead session is determined based on the prefix of the eventual consistency intent names in the subset. All eventual consistency intents of the dead session are retrieved from the subset of storage units, and execution of eventual consistency updates indicated in the all eventual consistency intents of the dead session is facilitated.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and more particularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/or store data. Such computing devices range from wireless smart phones, laptops, tablets, personal computers (PC), work stations, and video game devices, to data centers that support millions of web searches, stock trades, or on-line purchases every day. In general, a computing device includes a central processing unit (CPU), a memory system, user input/output interfaces, peripheral device interfaces, and an interconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using “cloud computing” to perform one or more computing functions (e.g., a service, an application, an algorithm, an arithmetic logic function, etc.) on behalf of the computer. Further, for large services, applications, and/or functions, cloud computing may be performed by multiple cloud computing resources in a distributed manner to improve the response time for completion of the service, application, and/or function. For example, Hadoop is an open source software framework that supports distributed applications enabling application execution by thousands of computers.

In addition to cloud computing, a computer may use “cloud storage” as part of its memory system. As is known, cloud storage enables a user, via its computer, to store files, applications, etc. on an Internet storage system. The Internet storage system may include a RAID (redundant array of independent disks) system and/or a dispersed storage system that uses an error correction scheme to encode data for storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed or distributed storage network (DSN) in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing core in accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an error encoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an error encoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of an encoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an error decoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of a decentralized agreement module in accordance with the present invention.

FIG. 10 is a schematic block diagram of an embodiment of a dispersed or distributed storage network (DSN) in accordance with the present invention; and

FIG. 11 is a logic diagram of an example of a method of eventual consistency intent cleanup in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, or distributed, storage network (DSN) 10 that includes a plurality of computing devices 12-16, a managing unit 18, an integrity processing unit 20, and a DSN memory 22. The components of the DSN 10 are coupled to a network 24, which may include one or more wireless and/or wire lined communication systems; one or more non-public intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may be located at geographically different sites (e.g., one in Chicago, one in Milwaukee, etc.), at a common site, or a combination thereof. For example, if the DSN memory 22 includes eight storage units 36, each storage unit is located at a different site. As another example, if the DSN memory 22 includes eight storage units 36, all eight storage units are located at the same site. As yet another example, if the DSN memory 22 includes eight storage units 36, a first pair of storage units are at a first common site, a second pair of storage units are at a second common site, a third pair of storage units are at a third common site, and a fourth pair of storage units are at a fourth common site. Note that a DSN memory 22 may include more or less than eight storage units 36. Further note that each storage unit 36 includes a computing core (as shown in FIG. 2, or components thereof) and a plurality of memory devices for storing dispersed error encoded data.

In various embodiments, each of the storage units operates as a distributed storage and task (DST) execution unit, and is operable to store dispersed error encoded data and/or to execute, in a distributed manner, one or more tasks on data. The tasks may be a simple function (e.g., a mathematical function, a logic function, an identify function, a find function, a search engine function, a replace function, etc.), a complex function (e.g., compression, human and/or computer language translation, text-to-voice conversion, voice-to-text conversion, etc.), multiple simple and/or complex functions, one or more algorithms, one or more applications, etc. Hereafter, a storage unit may be interchangeably referred to as a dispersed storage and task (DST) execution unit and a set of storage units may be interchangeably referred to as a set of DST execution units.

Each of the computing devices 12-16, the managing unit 18, and the integrity processing unit 20 include a computing core 26, which includes network interfaces 30-33. Computing devices 12-16 may each be a portable computing device and/or a fixed computing device. A portable computing device may be a social networking device, a gaming device, a cell phone, a smart phone, a digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a tablet, a video game controller, and/or any other portable device that includes a computing core. A fixed computing device may be a computer (PC), a computer server, a cable set-top box, a satellite receiver, a television set, a printer, a fax machine, home entertainment equipment, a video game console, and/or any type of home or office computing equipment. Note that each managing unit 18 and the integrity processing unit 20 may be separate computing devices, may be a common computing device, and/or may be integrated into one or more of the computing devices 12-16 and/or into one or more of the storage units 36. In various embodiments, computing devices 12-16 can include user devices and/or can be utilized by a requesting entity generating access requests, which can include requests to read or write data to storage units in the DSN.

Each interface 30, 32, and 33 includes software and hardware to support one or more communication links via the network 24 indirectly and/or directly. For example, interface 30 supports a communication link (e.g., wired, wireless, direct, via a LAN, via the network 24, etc.) between computing devices 14 and 16. As another example, interface 32 supports communication links (e.g., a wired connection, a wireless connection, a LAN connection, and/or any other type of connection to/from the network 24) between computing devices 12 & 16 and the DSN memory 22. As yet another example, interface 33 supports a communication link for each of the managing unit 18 and the integrity processing unit 20 to the network 24.

Computing devices 12 and 16 include a dispersed storage (DS) client module 34, which enables the computing device to dispersed storage error encode and decode data as subsequently described with reference to one or more of FIGS. 3-8. In this example embodiment, computing device 16 functions as a dispersed storage processing agent for computing device 14. In this role, computing device 16 dispersed storage error encodes and decodes data on behalf of computing device 14. With the use of dispersed storage error encoding and decoding, the DSN 10 is tolerant of a significant number of storage unit failures (the number of failures is based on parameters of the dispersed storage error encoding function) without loss of data and without the need for a redundant or backup copies of the data. Further, the DSN 10 stores data for an indefinite period of time without data loss and in a secure manner (e.g., the system is very resistant to unauthorized attempts at accessing the data).

In operation, the managing unit 18 performs DS management services. For example, the managing unit 18 establishes distributed data storage parameters (e.g., vault creation, distributed storage parameters, security parameters, billing information, user profile information, etc.) for computing devices 12-14 individually or as part of a group of user devices. As a specific example, the managing unit 18 coordinates creation of a vault (e.g., a virtual memory block associated with a portion of an overall namespace of the DSN) within the DSN memory 22 for a user device, a group of devices, or for public access and establishes per vault dispersed storage (DS) error encoding parameters for a vault. The managing unit 18 facilitates storage of DS error encoding parameters for each vault by updating registry information of the DSN 10, where the registry information may be stored in the DSN memory 22, a computing device 12-16, the managing unit 18, and/or the integrity processing unit 20.

The DSN managing unit 18 creates and stores user profile information (e.g., an access control list (ACL)) in local memory and/or within memory of the DSN memory 22. The user profile information includes authentication information, permissions, and/or the security parameters. The security parameters may include encryption/decryption scheme, one or more encryption keys, key generation scheme, and/or data encoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particular user, a user group, a vault access, public vault access, etc. For instance, the DSN managing unit 18 tracks the number of times a user accesses a non-public vault and/or public vaults, which can be used to generate a per-access billing information. In another instance, the DSN managing unit 18 tracks the amount of data stored and/or retrieved by a user device and/or a user group, which can be used to generate a per-data-amount billing information.

As another example, the managing unit 18 performs network operations, network administration, and/or network maintenance. Network operations includes authenticating user data allocation requests (e.g., read and/or write requests), managing creation of vaults, establishing authentication credentials for user devices, adding/deleting components (e.g., user devices, storage units, and/or computing devices with a DS client module 34) to/from the DSN 10, and/or establishing authentication credentials for the storage units 36. Network administration includes monitoring devices and/or units for failures, maintaining vault information, determining device and/or unit activation status, determining device and/or unit loading, and/or determining any other system level operation that affects the performance level of the DSN 10. Network maintenance includes facilitating replacing, upgrading, repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missing encoded data slices. At a high level, the integrity processing unit 20 performs rebuilding by periodically attempting to retrieve/list encoded data slices, and/or slice names of the encoded data slices, from the DSN memory 22. For retrieved encoded slices, they are checked for errors due to data corruption, outdated version, etc. If a slice includes an error, it is flagged as a ‘bad’ slice. For encoded data slices that were not received and/or not listed, they are flagged as missing slices. Bad and/or missing slices are subsequently rebuilt using other retrieved encoded data slices that are deemed to be good slices to produce rebuilt slices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core 26 that includes a processing module 50, a memory controller 52, main memory 54, a video graphics processing unit 55, an input/output (I/O) controller 56, a peripheral component interconnect (PCI) interface 58, an IO interface module 60, at least one IO device interface module 62, a read only memory (ROM) basic input output system (BIOS) 64, and one or more memory interface modules. The one or more memory interface module(s) includes one or more of a universal serial bus (USB) interface module 66, a host bus adapter (HBA) interface module 68, a network interface module 70, a flash interface module 72, a hard drive interface module 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), interne small computer system interface (iSCSI), etc.). The DSN interface module 76 and/or the network interface module 70 may function as one or more of the interface 30-33 of FIG. 1. Note that the IO device interface module 62 and/or the memory interface modules 66-76 may be collectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data. When a computing device 12 or 16 has data to store it disperse storage error encodes the data in accordance with a dispersed storage error encoding process based on dispersed storage error encoding parameters. Here, the computing device stores data object 40, which can include a file (e.g., text, video, audio, etc.), or other data arrangement. The dispersed storage error encoding parameters include an encoding function (e.g., information dispersal algorithm (IDA), Reed-Solomon, Cauchy Reed-Solomon, systematic encoding, non-systematic encoding, on-line codes, etc.), a data segmenting protocol (e.g., data segment size, fixed, variable, etc.), and per data segment encoding values. The per data segment encoding values include a total, or pillar width, number (T) of encoded data slices per encoding of a data segment i.e., in a set of encoded data slices); a decode threshold number (D) of encoded data slices of a set of encoded data slices that are needed to recover the data segment; a read threshold number (R) of encoded data slices to indicate a number of encoded data slices per set to be read from storage for decoding of the data segment; and/or a write threshold number (W) to indicate a number of encoded data slices per set that must be accurately stored before the encoded data segment is deemed to have been properly stored. The dispersed storage error encoding parameters may further include slicing information (e.g., the number of encoded data slices that will be created for each data segment) and/or slice security information (e.g., per encoded data slice encryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as the encoding function (a generic example is shown in FIG. 4 and a specific example is shown in FIG. 5); the data segmenting protocol is to divide the data object into fixed sized data segments; and the per data segment encoding values include: a pillar width of 5, a decode threshold of 3, a read threshold of 4, and a write threshold of 4. In accordance with the data segmenting protocol, the computing device 12 or 16 divides data object 40 into a plurality of fixed sized data segments (e.g., 1 through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more). The number of data segments created is dependent of the size of the data and the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a data segment using the selected encoding function (e.g., Cauchy Reed-Solomon) to produce a set of encoded data slices. FIG. 4 illustrates a generic Cauchy Reed-Solomon encoding function, which includes an encoding matrix (EM), a data matrix (DM), and a coded matrix (CM). The size of the encoding matrix (EM) is dependent on the pillar width number (T) and the decode threshold number (D) of selected per data segment encoding values. To produce the data matrix (DM), the data segment is divided into a plurality of data blocks and the data blocks are arranged into D number of rows with Z data blocks per row. Note that Z is a function of the number of data blocks created from the data segment and the decode threshold number (D). The coded matrix is produced by matrix multiplying the data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encoding with a pillar number (T) of five and decode threshold number of three. In this example, a first data segment is divided into twelve data blocks (D1-D12). The coded matrix includes five rows of coded data blocks, where the first row of X11-X14 corresponds to a first encoded data slice (EDS 1_1), the second row of X21-X24 corresponds to a second encoded data slice (EDS 2_1), the third row of X31-X34 corresponds to a third encoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to a fourth encoded data slice (EDS 4_1), and the fifth row of X51-X54 corresponds to a fifth encoded data slice (EDS 5_1). Note that the second number of the EDS designation corresponds to the data segment number.

Returning to the discussion of FIG. 3, the computing device also creates a slice name (SN) for each encoded data slice (EDS) in the set of encoded data slices. A typical format for a slice name 80 is shown in FIG. 6. As shown, the slice name (SN) 80 includes a pillar number of the encoded data slice (e.g., one of 1-T), a data segment number (e.g., one of 1-Y), a vault identifier (ID), a data object identifier (ID), and may further include revision level information of the encoded data slices. The slice name functions as, at least part of, a DSN address for the encoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces a plurality of sets of encoded data slices, which are provided with their respective slice names to the storage units for storage. As shown, the first set of encoded data slices includes EDS 1_1 through EDS 5_1 and the first set of slice names includes SN 1_1 through SN 5_1 and the last set of encoded data slices includes EDS 1_Y through EDS 5_Y and the last set of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of a data object that was dispersed storage error encoded and stored in the example of FIG. 4. In this example, the computing device 12 or 16 retrieves from the storage units at least the decode threshold number of encoded data slices per data segment. As a specific example, the computing device retrieves a read threshold number of encoded data slices.

To recover a data segment from a decode threshold number of encoded data slices, the computing device uses a decoding function as shown in FIG. 8. As shown, the decoding function is essentially an inverse of the encoding function of FIG. 4. The coded matrix includes a decode threshold number of rows (e.g., three in this example) and the decoding matrix in an inversion of the encoding matrix that includes the corresponding rows of the coded matrix. For example, if the coded matrix includes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2, and 4, and then inverted to produce the decoding matrix.

FIG. 9 is a schematic block diagram of an embodiment of a decentralized agreement module 910 that includes a set of deterministic functions 1-N, a set of normalizing functions 1-N, a set of scoring functions 1-N, and a ranking function. Each of the deterministic function, the normalizing function, the scoring function, and the ranking function, may be implemented utilizing, for example, processing module 50 of the computing core 26. The decentralized agreement module may be implemented utilizing any module and/or unit of a dispersed storage network (DSN). For example, the decentralized agreement module is implemented utilizing the distributed storage and task (DST) client module 34 of FIG. 1.

The decentralized agreement module functions to receive a ranked scoring information request and to generate ranked scoring information based on the ranked scoring information request and other information. The ranked scoring information request includes one or more of an asset identifier (ID) of an asset associated with the request, an asset type indicator, one or more location identifiers of locations associated with the DSN, one or more corresponding location weights, and a requesting entity ID. The asset includes any portion of data associated with the DSN including one or more asset types including a data object, a data record, an encoded data slice, a data segment, a set of encoded data slices, and a plurality of sets of encoded data slices. As such, the asset ID of the asset includes one or more of a data name, a data record identifier, a source name, a slice name, and a plurality of sets of slice names.

Each location of the DSN includes an aspect of a DSN resource. Examples of locations includes one or more of a storage unit, a memory device of the storage unit, a site, a storage pool of storage units, a pillar index associated with each encoded data slice of a set of encoded data slices generated by an information dispersal algorithm (IDA), a DS client module 34 of FIG. 1, a computing device 16 of FIG. 1, an integrity processing unit 20 of FIG. 1, a managing unit 18 of FIG. 1, a computing device 12 of FIG. 1, and a computing device 14 of FIG. 1.

Each location is associated with a location weight based on one or more of a resource prioritization of utilization scheme and physical configuration of the DSN. The location weight includes an arbitrary bias which adjusts a proportion of selections to an associated location such that a probability that an asset will be mapped to that location is equal to the location weight divided by a sum of all location weights for all locations of comparison. For example, each storage pool of a plurality of storage pools is associated with a location weight based on storage capacity. For instance, storage pools with more storage capacity are associated with higher location weights than others. The other information may include a set of location identifiers and a set of location weights associated with the set of location identifiers. For example, the other information includes location identifiers and location weights associated with a set of memory devices of a storage unit when the requesting entity utilizes the decentralized agreement module to produce ranked scoring information with regards to selection of a memory device of the set of memory devices for accessing a particular encoded data slice (e.g., where the asset ID includes a slice name of the particular encoded data slice).

The decentralized agreement module outputs substantially identical ranked scoring information for each ranked scoring information request that includes substantially identical content of the ranked scoring information request. For example, a first requesting entity issues a first ranked scoring information request to the decentralized agreement module and receives first ranked scoring information. A second requesting entity issues a second ranked scoring information request to the decentralized agreement module and receives second ranked scoring information. The second ranked scoring information is substantially the same as the first ranked scoring information when the second ranked scoring information request is substantially the same as the first ranked scoring information request.

As such, two or more requesting entities may utilize the decentralized agreement module to determine substantially identical ranked scoring information. As a specific example, the first requesting entity selects a first storage pool of a plurality of storage pools for storing a set of encoded data slices utilizing the decentralized agreement module and the second requesting entity identifies the first storage pool of the plurality of storage pools for retrieving the set of encoded data slices utilizing the decentralized agreement module.

In an example of operation, the decentralized agreement module receives the ranked scoring information request. Each deterministic function performs a deterministic function on a combination and/or concatenation (e.g., add, append, interleave) of the asset ID of the request and an associated location ID of the set of location IDs to produce an interim result. The deterministic function includes at least one of a hashing function, a hash-based message authentication code function, a mask generating function, a cyclic redundancy code function, hashing module of a number of locations, consistent hashing, rendezvous hashing, and a sponge function. As a specific example, deterministic function 2 appends a location ID 2 of a storage pool 2 to a source name as the asset ID to produce a combined value and performs the mask generating function on the combined value to produce interim result 2.

With a set of interim results 1-N, each normalizing function performs a normalizing function on a corresponding interim result to produce a corresponding normalized interim result. The performing of the normalizing function includes dividing the interim result by a number of possible permutations of the output of the deterministic function to produce the normalized interim result. For example, normalizing function 2 performs the normalizing function on the interim result 2 to produce a normalized interim result 2.

With a set of normalized interim results 1-N, each scoring function performs a scoring function on a corresponding normalized interim result to produce a corresponding score. The performing of the scoring function includes dividing an associated location weight by a negative log of the normalized interim result. For example, scoring function 2 divides location weight 2 of the storage pool 2 (e.g., associated with location ID 2) by a negative log of the normalized interim result 2 to produce a score 2.

With a set of scores 1-N, the ranking function performs a ranking function on the set of scores 1-N to generate the ranked scoring information. The ranking function includes rank ordering each score with other scores of the set of scores 1-N, where a highest score is ranked first. As such, a location associated with the highest score may be considered a highest priority location for resource utilization (e.g., accessing, storing, retrieving, etc., the given asset of the request). Having generated the ranked scoring information, the decentralized agreement module outputs the ranked scoring information to the requesting entity.

FIG. 10 is a schematic block diagram of another embodiment of a dispersed storage network (DSN) that includes that includes a dispersed storage (DS) cleanup unit 1010, at least one computing device 16 of FIG. 1, the network 24 of FIG. 1, and a plurality of storage sets 1-k that each include a plurality of storage units 1-n. Each storage set can contain the same number or a different number of storage units. Each storage unit may be implemented utilizing the storage unit 36 of FIG. 1. The DS cleanup unit can include the interface 30, 32, or 33 of FIG. 1, computing core 26 of FIG. 1, and/or the DS client module 34 of FIG. 1. The DS cleanup unit can also include the decentralized agreement module 910 of FIG. 9. The DS cleanup unit can also be implemented by utilizing computing device 12-16, management unit 18, storage unit 36, and/or integrity processing unit 20 of FIG. 1. The DS cleanup unit can communicate with one or more of computing device 12, 14 and/or 16, management unit 18, and/or integrity processing unit 20 of FIG. 1 via network 24, for example, to determine sessions that are dead, retrieve eventual consistency intents from storage unit, facilitate execution of eventual consistency updates, and/or to execute other functions as described herein. The computing device 16 can include the decentralized agreement module 910 of FIG. 9, and can function as a dispersed storage processing agent for computing device 14 as described previously, and will herein be interchangeably referred to as a DSN processing unit. The DSN functions to clean eventual consistency intent.

Eventual Consistency Intents (ECIs) are small objects that can be stored in a DSN memory to ensure that a piece of work eventually gets done. A DSN processing unit, such as computing device 16, can write these intents to memory along with an immediate consistency update, and can return a response to a user before moving on to processing the eventual consistency update. Once the DSN processing unit finishes the eventual consistency update in the background, it can delete the intent from the DSN memory. If, however, the DSN processing unit crashes or runs into a network partition which prevents it from accomplishing the update, the intent will be left in DSN memory. Intents which are left behind are later discovered and executed by a cleanup agent, such as DS cleanup unit 1010.

Intent cleanup scanning can be an efficient process if the names of the intents are chosen wisely. Cleanup agents only need to scan for intents that are associated with dead sessions, so the process of finding all intents for a given session ID should be optimized. This optimization can be made possible by prefixing intent names with their associated session ID, so that prefix-based listing can be done to quickly find all intents for a dead session. For example, a DSN processing unit, upon creating an eventual consistency intent to be written to memory, can prefix the session ID in the intent name it generates.

Furthermore, a name generation scheme can be used to achieve storage set locality, ensuring that intents of the same session ID are stored in the same storage set. While FIG. 10 depicts only storage set locality, the name generation scheme can be used to achieve “stripe” locality within a storage set, where a stripe of storage units corresponds to a subset of storage units in a storage set that store data slices corresponding to the same data object, the same set of data objects, and/or the same data source. The storage units in a stripe are determined as a result of, for example, encoding the data based on the utilizing the dispersed storage error encoding scheme and corresponding parameters and/or based on the hashing scheme used to select storage units within a storage set to store encoded data. Stripe locality ensures that intents of the same session ID are stored in the same stripe of storage units within the storage set. In various embodiments, the name generation scheme can be based on a weighted rendezvous hash (WRH) strategy. A decentralized agreement protocol (DAP) can be utilized to generate names, and DSN processing units can utilize their own decentralized agreement module 910 or another decentralized agreement module to generate eventual consistency intent names, where eventual consistency intents of the same session are mapped to the same storage set and/or the same stripe of storage units in the storage set. For example, eventual consistency intent names are generated to include the session ID in the prefix as discussed previously A namespace mapping that determines where an intent will be stored can be based on the prefixes of eventual consistency intent names, and in particular, can ensure that intents of the same session ID are stored in the same storage set and/or same storage stripe of a storage set. The same namespace mapping scheme can be used by all DSN processing units to ensure naming consistency. Alternatively, the integrity processing unit, the managing unit, or another unit of the DSN that is globally accessible by all DSN processing units can be responsible for generating all the eventual consistency intent names.

Consider an example eventual consistency intent name generation scheme where the first 16 of 24 bytes in the storage name are used as input to the WRH. If this is the case, a name generation scheme which sets all 16 of these bytes to the same value for all intents in a session would result in all of those intents being stored in the same storage set. For this same DAP, consider that the stripe within the storage set is chosen based on a namespace mapping using the same 16 bytes. Since those bytes will be the same for all intents in the session, all of the eventual consistency intents of the session will all be stored in the same stripe.

The cleanup unit can utilize knowledge of the name generation scheme to determine the subset of storage units where all eventual consistency intents of a dead session are stored, for example, by determining the corresponding storage set and/or storage stripe based on the session identifier of the dead session and/or based on the prefixes of the ones of the identified eventual consistency intent names. Using a storage set and/or stripe locality based name generation scheme helps to ensure that intent cleanup by the cleanup unit is scalable. If the cleanup scanning algorithm required listing from all devices in the pool, it would become unwieldy as pool gets larger. The cleanup unit can retrieve the eventual consistency intents of the dead session, and can facilitate execution of the eventual consistency updates of these intents accordingly. For example, the cleanup unit can relay the update instructions to another DSN processing unit or other unit of the DSN, can instruct storage units to send the eventual consistency intents to another responsible DSN processing unit for processing, or can process and execute the update itself.

In various embodiments, a processing system of a dispersed storage (DS) cleanup unit of a DSN includes at least one processor and a memory that stores operational instructions, that when executed by the at least one processor cause the processing system to determine a dead session of the DSN. A subset of a plurality of eventual consistency intent names is generated by identifying ones of the plurality of eventual consistency intent names that include a session identifier corresponding to the dead session in a prefix of the ones of the plurality of eventual consistency intent names, where the subset of the plurality of eventual consistency intent names corresponds to all eventual consistency intents of the dead session. A subset of storage units responsible for storing the all eventual consistency intents of the dead session is determined based on the prefix of the ones of the plurality of eventual consistency intent names in the subset. All eventual consistency intents of the dead session are retrieved from the subset of storage units, and execution of eventual consistency updates indicated in the all eventual consistency intents of the dead session is facilitated.

In various embodiments, generating the subset of the plurality of eventual consistency intent names includes generating a prefixed-based listing of the plurality of eventual consistency intent names. In various embodiments, the session identifier in the prefix of the eventual consistency intent name maps to the subset of storage units, and the subset of storage units is determined based on the session identifier corresponding to the dead session included in the prefix. In various embodiments, all eventual consistency intents are stored in subsets of storage units mapped to their session identifier. In various embodiments, the DSN includes a plurality of storage sets, and the subset of storage units is located in a same one of the plurality of storage sets. In various embodiments, each storage set includes a plurality of stripes of storage units, and the subset of storage units is located in a same one of the plurality of storage stripes in the same one of the plurality of storage sets. In various embodiments, the plurality of eventual consistency intent names is generated by utilizing a name generation scheme based on a weighted rendezvous strategy.

In various embodiments, the session is associated with a computing device of the DSN, and the session is determined to be dead when the computing device crashes. In various embodiments, the session is determined to be dead when the computing device runs into a network partition which prevents it from accomplishing the eventual consistency update. In various embodiments, the session is determined to be dead in response to receiving a notification via a network of the DSN.

FIG. 11 is a flowchart illustrating an example of eventual consistency intent cleanup. In particular, a method is presented for use in association with one or more functions and features described in conjunction with FIGS. 1-10, for execution by a dispersed storage (DS) cleanup unit that includes a processor or via another processing system of a dispersed storage network that includes at least one processor and memory that stores instruction that configure the processor or processors to perform the steps described below.

Step 1102 includes determining a dead session of a DSN associated with the DS cleanup unit. For example, sessions can be associated with computing devices of the DSN, and the cleanup unit can determine a session is dead when the associated computing device crashes or runs into a network partition which prevents it from accomplishing the update. In various embodiments, the cleanup unit can determine a session is dead response to receiving a notification via a network of the DSN.

Step 1104 includes generating a subset of a plurality of eventual consistency intent names by identifying ones of the plurality of eventual consistency intent names that include a session identifier corresponding to the dead session in a prefix of the ones of the plurality of eventual consistency intent names, where the subset of the plurality of eventual consistency intent names corresponds to all eventual consistency intents of the dead session. Generating the subset of the plurality of eventual consistency intent names can include generating a prefixed-based listing of the plurality of eventual consistency intent names. The eventual consistency intent names can be generated by utilizing a name generation scheme based on a weighted rendezvous strategy.

Step 1106 include determining a subset of storage units responsible for storing the all eventual consistency intents of the dead session based on the prefix of the ones of the plurality of eventual consistency intent names in the subset. The session identifier in the prefix of the eventual consistency intent name can map to the subset of storage units, and the subset of storage units can be determined based on the session identifier corresponding to the dead session included in the prefix. In various embodiments, all eventual consistency intents are stored in subsets of storage units mapped to their session identifier. For example, the determined subset of storage units can be located in the same storage set based on the prefix and/or the determined subset of storage units can be located in a same stripe of the same storage set based on the prefix.

Step 1108 includes retrieving the all eventual consistency intents of the dead session from the determined subset of storage units. Step 1110 facilitating execution of eventual consistency updates indicated in the all eventual consistency intents of the dead session.

In various embodiments, a non-transitory computer readable storage medium includes at least one memory section that stores operational instructions that, when executed by a processing system of a dispersed storage network (DSN) that includes a processor and a memory, causes the processing system to determine a dead session of the DSN. A subset of a plurality of eventual consistency intent names is generated by identifying ones of the plurality of eventual consistency intent names that include a session identifier corresponding to the dead session in a prefix of the ones of the plurality of eventual consistency intent names, where the subset of the plurality of eventual consistency intent names corresponds to all eventual consistency intents of the dead session. A subset of storage units responsible for storing the all eventual consistency intents of the dead session is determined based on the prefix of the ones of the plurality of eventual consistency intent names in the subset. All eventual consistency intents of the dead session are retrieved from the subset of storage units, and execution of eventual consistency updates indicated in the all eventual consistency intents of the dead session is facilitated.

It is noted that terminologies as may be used herein such as bit stream, stream, signal sequence, etc. (or their equivalents) have been used interchangeably to describe digital information whose content corresponds to any of a number of desired types (e.g., data, video, speech, audio, etc. any of which may generally be referred to as ‘data’).

As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “configured to”, “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for an example of indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “configured to”, “operable to”, “coupled to”, or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1. As may be used herein, the term “compares unfavorably”, indicates that a comparison between two or more items, signals, etc., fails to provide the desired relationship.

As may also be used herein, the terms “processing module”, “processing circuit”, “processor”, and/or “processing unit” may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may be, or further include, memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of another processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the Figures. Such a memory device or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claims. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claims. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.

In addition, a flow diagram may include a “start” and/or “continue” indication. The “start” and “continue” indications reflect that the steps presented can optionally be incorporated in or otherwise used in conjunction with other routines. In this context, “start” indicates the beginning of the first step presented and may be preceded by other activities not specifically shown. Further, the “continue” indication reflects that the steps presented may be performed multiple times and/or may be succeeded by other activities not specifically shown. Further, while a flow diagram indicates a particular ordering of steps, other orderings are likewise possible provided that the principles of causality are maintained.

The one or more embodiments are used herein to illustrate one or more aspects, one or more features, one or more concepts, and/or one or more examples. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of the embodiments. A module implements one or more functions via a device such as a processor or other processing device or other hardware that may include or operate in association with a memory that stores operational instructions. A module may operate independently and/or in conjunction with software and/or firmware. As also used herein, a module may contain one or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes one or more memory elements. A memory element may be a separate memory device, multiple memory devices, or a set of memory locations within a memory device. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. The memory device may be in a form a solid state memory, a hard drive memory, cloud memory, thumb drive, server memory, computing device memory, and/or other physical medium for storing digital information.

While particular combinations of various functions and features of the one or more embodiments have been expressly described herein, other combinations of these features and functions are likewise possible. The present disclosure is not limited by the particular examples disclosed herein and expressly incorporates these other combinations. 

What is claimed is:
 1. A method for execution by a dispersed storage (DS) cleanup unit of a dispersed storage network (DSN) that includes a processor, the method comprises: determining a dead session of the DSN; generating a subset of a plurality of eventual consistency intent names by identifying ones of the plurality of eventual consistency intent names that include a session identifier corresponding to the dead session in a prefix of the ones of the plurality of eventual consistency intent names, wherein the subset of the plurality of eventual consistency intent names corresponds to all eventual consistency intents of the dead session; determining a subset of storage units responsible for storing the all eventual consistency intents of the dead session based on the prefix of the eventual consistency intent names in the sub set; retrieving the all eventual consistency intents of the dead session from the subset of storage units; and facilitating execution of eventual consistency updates indicated in the all eventual consistency intents of the dead session.
 2. The method of claim 1, wherein generating the subset of the plurality of eventual consistency intent names includes generating a prefixed-based listing of the plurality of eventual consistency intent names.
 3. The method of claim 1, wherein the session identifier in the prefix of each of the plurality of eventual consistency intent names maps to the subset of storage units, and wherein the subset of storage units is determined based on the session identifier corresponding to the dead session included in the prefix.
 4. The method of claim 3, wherein the all eventual consistency intents of the dead session are stored in subsets of storage units mapped to the session identifier corresponding to the dead session.
 5. The method of claim 1, wherein the DSN includes a plurality of storage sets, and wherein the subset of storage units is located in a same one of the plurality of storage sets.
 6. The method of claim 5, wherein each storage set includes a plurality of stripes of storage units, and wherein the subset of storage units is located in a same one of the plurality of storage stripes in the same one of the plurality of storage sets.
 7. The method of claim 1, wherein the plurality of eventual consistency intent names is generated by utilizing a name generation scheme based on a weighted rendezvous strategy.
 8. The method of claim 1, wherein the dead session is associated with a computing device of the DSN, and wherein the dead session is determined based on the computing device crashing.
 9. The method of claim 1, wherein the dead session is associated with a computing device of the DSN, and wherein the dead session is determined based on when the computing device encounters a network partition which prevents the computing device from accomplishing an eventual consistency update.
 10. The method of claim 1, wherein the dead session is determined in response to receiving a notification via a network of the DSN.
 11. A processing system of a dispersed storage (DS) cleanup unit comprises: at least one processor; a memory that stores operational instructions, that when executed by the at least one processor cause the processing system to: determine a dead session of a DSN associated with the DS cleanup unit; generate a subset of a plurality of eventual consistency intent names by identifying ones of the plurality of eventual consistency intent names that include a session identifier corresponding to the dead session in a prefix of the ones of the plurality of eventual consistency intent names, wherein the subset of the plurality of eventual consistency intent names corresponds to all eventual consistency intents of the dead session; determine a subset of storage units responsible for storing the all eventual consistency intents of the dead session based on the prefix of the eventual consistency intent names in the subset; retrieve the all eventual consistency intents of the dead session from the subset of storage units; and facilitate execution of eventual consistency updates indicated in the all eventual consistency intents of the dead session.
 12. The processing system of claim 11, wherein generating the subset of the plurality of eventual consistency intent names includes generating a prefixed-based listing of the plurality of eventual consistency intent names.
 13. The processing system of claim 11, wherein the session identifier in the prefix of each of the plurality of eventual consistency intent names maps to the subset of storage units, and wherein the subset of storage units is determined based on the session identifier corresponding to the dead session included in the prefix.
 14. The processing system of claim 13, wherein the all eventual consistency intents of the dead session are stored in subsets of storage units mapped to their session identifier corresponding to the dead session.
 15. The processing system of claim 11, wherein the DSN includes a plurality of storage sets, and wherein the subset of storage units is located in a same one of the plurality of storage sets.
 16. The processing system of claim 15, wherein each storage set includes a plurality of stripes of storage units, and wherein the subset of storage units is located in a same one of the plurality of storage stripes in the same one of the plurality of storage sets.
 17. The processing system of claim 11, wherein the plurality of eventual consistency intent names is generated by utilizing a name generation scheme based on a weighted rendezvous strategy.
 18. The processing system of claim 11, wherein the dead session is associated with a computing device of the DSN, and wherein the dead session is determined based on when the computing device crashing.
 19. The processing system of claim 11, wherein the dead session is associated with a computing device of the DSN, and wherein the dead session is determined based on when the computing device encounters a network partition which prevents the computing device from accomplishing the eventual consistency update.
 20. A non-transitory computer readable storage medium comprises: at least one memory section that stores operational instructions that, when executed by a processing system of a dispersed storage network (DSN) that includes a processor and a memory, causes the processing system to: determine a dead session of the DSN; generate a subset of a plurality of eventual consistency intent names by identifying ones of the plurality of eventual consistency intent names that include a session identifier corresponding to the dead session in a prefix of the ones of the plurality of eventual consistency intent names, wherein the subset of the plurality of eventual consistency intent names corresponds to all eventual consistency intents of the dead session; determine a subset of storage units responsible for storing the all eventual consistency intents of the dead session based on the prefix of the eventual consistency intent names in the subset; retrieve the all eventual consistency intents of the dead session from the subset of storage units; and facilitate execution of eventual consistency updates indicated in the all eventual consistency intents of the dead session. 